I've had that happen a couple times on me too. I've normally found some other issue with the model, and evenuallly it went away, and I was able to see the item in the 3D viewer correctly. My guess is something might be wrong with the model. Looking at the render, I see some polygons that look strange, possibly inverted or bad normals. Mainly on the very front surface, I see a triangle that seems to be shading incorreclty to my eye. If you want to post the model, I'm sure several of us can help check it out. Post a .stl if possible.

If i change all the outward facing normals to inward then i get the error:
Unfortunately, we were not able to process and thus print your model. The error message received is the following "Only manifold objects can be printed".

The first model had all normals flipped and several errors.
By reversing all normals, at least it looks ok in meshlab, and meshmedic (shapeways upload fix thingy) is then apparently able to fix it.

I used meshlab 1.2.3b,l loaded the file, and then : menu filters -> normals,curvature.... -> Invert faces orientation, I think I used the original STL.
(guidline in meshlab : the real dark faces are usually inside out, the whiter ones are ok.)

The last wrl file is partly dark partly white, indicating mixed normals.
There is plenty other options, also a re-orient all faces coherently.
But I'm not sure how you got the model partly inside out like the last example ?